Technical Field
The invention relates to the detection of one or more analytes in a sample or a series of samples. More particularly, the invention relates to a method for determining one or more biological elements, e.g., biological cells, in a population of biological elements.
Related Art
Using conventional technologies, biological libraries may be screened for components containing, for example, cells, antibodies, proteins, peptides and, nucleic acids. These technologies include phage display, ribosome display, yeast, bacterial display, in vitro compartmentalization, microengraving and spatial addressing. Such systems have a number of disadvantages, including the need to enrich for desired clones via repeat selection steps (including, for example “panning”) that inherently result in the loss of potential binding candidates. It is also difficult to establish the precise origin of a positive signal using conventional technologies since they obtain mixed signals from heterogeneous populations that cannot be deconvoluted. Generally these techniques involve selection processes utilizing bacteriophages, ribosomes and specific cells, most of which are performed in vitro.
Improvements in library screening have introduced the concept of spatial addressing in order to maintain identity of the screened components during the selection process. Such addressing can be based upon techniques including robotics, enzyme-linked immunosorbent assays, or cell-based assays. While spatial addressing can, for example, identify specific cellular clones to generate master stocks, these approaches do not facilitate high throughput screening techniques to selectively isolate and purify the identified clones for rapid application to disease diagnostics and therapeutics. Another disadvantage of the present screening assays is that they are usually limited to a cell number between approximately 50 and 100 thousand.
For performing cell-based screening, one of the particular challenges is the isolation of small populations of cells in a manner that allows for subsequent screening procedures. Traditional devices and methods of isolating cells do not adequately provide for the isolation of small populations of cells without performing steps that potentially modify cellular function or activity. Isolation of cells is not only important in screening, but also in processes that involve the monitoring, measuring, and/or use of the output of cellular activity or function (e.g., antibody production) for small populations of cells.
Accordingly, the need to isolate small numbers of specific cells from background populations is ubiquitous, with applications in pathology, clinical diagnosis, cloning, and cell biology research. Current screening methods have numerous technical challenges, including: the size of protein displayed has to be small, the multiplicity of infection (MOI) needs to be high to avoid loss of diversity, the dependency on the activity of the phage, multiple panning rounds are needed (taking up to 1 week or more), high non-specific binding due to phage, antibodies may not function well in soluble form (truncated clones are often expressed), and/or avidity effects can hinder selection of high affinity clones.
Accordingly, the inventors have identified a need in the art for a more efficient process of identifying, isolating and characterizing components of biological populations.